You need a 55% alcohol solution. on hand, you have a 330 ml of a 80% alcohol mixture. how much pure water will you need to add to obtain the desired solution?

you will
ml of pure water
to
ml of the desired 55% solution.

y = amount needed at 55% alcohol.

x = amount of pure water, or 0% alcohol

so, you have on hand 330 mL of 80% alcohol, so how much alcohol only is there on that mixture?  well, is 330 mL, so 80% of 330 is 330 * (80/100)  = 330 * 0.8 = 264 mL.

likewise, let's convert the other perecentage values to deciaml, bearing in mind that pure water is, well just pure water, it has no alcohol, or we can say that it has 0% alcohol.

215.92 dollars is the answer